898
FXUS66 KMFR 060524
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
1024 PM PDT Sun May 5 2024

...New Aviation Section...


.AVIATION (06Z TAFs)...

VFR conditions are expected at the terminals through early parts
of this cycle, but an approaching front may tilt the odds in favor
of MVFR. Confidence is highest (~70%) for North Bend to reach
MVFR ceilings, but timing on that is going to be tough to nail
down. That said, all the terminals will be within a couple
thousand feet of MVFR, so low clouds in general are expected
through this cycle. Additionally, light rain showers are expected
through this cycle. The front will also bring breezy conditions
on the eastside which will impact Klamath Falls tomorrow
afternoon.

-Guerrero

&&

.PREV DISCUSSION... /Issued 831 PM PDT Sun May 5 2024/

DISCUSSION...Showers are tapering off this evening, though some
linger over the Cascades. These dry(-ish) conditions in the region
will be brief, as the next frontal system is visible around 100 NM
offshore. Despite this incoming precipitation (and the increase
cloudiness associated with it), conditions will stay clear enough
in northern CA (and in the Rogue) that temperatures on the
chillier side are expected overnight. While conditions will remain
above freezing in the Rogue Valley, another Freeze Warning is in
place for the Shasta and Scott valleys for early Monday morning.

The front will makes its gradual way inland overnight into Monday,
bringing light to moderate precipitation to the area and breezy
west winds, especially to northern Lake County where a Wind
Advisory begins at 11 AM Monday. For more details on the forecast,
please see the previous discussion below.
-CSP

AVIATION...05/18Z TAFs... A period of VFR will ensue until the
front arrives later tonight. Once the front arrives, we will see
precipitation chances return and MVFR conditions. North Bend is the
most likely (~70%) terminal to reach MVFR, but the other terminals
will be close at ~30-50% chances for MVFR conditions. Precipitation
will be mostly in the form of rain showers, and coverage is expected
to be isolated across the area. Lastly, the eastside of the Cascades
will be breezy, so expect Klamath Falls to see sustained wind speeds
around 20 mph gusting to around 30 mph both this afternoon and
tomorrow afternoon.

-Guerrero

MARINE...Updated 830 PM Sunday, May 5, 2024...Seas will become more
chaotic as another front moves through tonight into early Monday
morning. The resulting southwest winds are not expected to reach
gale force conditions, but moderate swell-dominated seas follow
Monday into Tuesday. A thermal trough will develop Tuesday afternoon
with gusty north winds and steep wind-driven seas, strongest south
of Cape Blanco. Wind speeds will peak late Wednesday, but strong
northerly winds will persist into Thursday night. During this
stretch (Tues-Wed) we could see gale force winds come to fruition,
especially across the southern waters. The thermal trough will
weaken Friday into next weekend.

-Guerrero

PREV DISCUSSION... /Issued 249 PM PDT Sun May 5 2024/

SHORT TERM...Through Wednesday morning...Upper flow aloft around a
low pressure system to the east of our area counties to bring
showery activity across northern California and southern Oregon. For
this afternoon, radar indicates that a wide area of showers remains
over Lake, Modoc, and eastern Klamath counties with generally
scattered showers elsewhere. This activity will decrease steadily
overnight, with 20-40% chances of showers remaining over the Coos
County coast and the Cascades through this evening.

Cold overnight temperatures remain in the forecast for Monday
morning. There is high confidence in the temperatures for the Shasta
and Scott valleys returning to at or below freezing tonight. A
Freeze Warning has been issued for these areas from 2 AM through 9
AM on Monday morning to communicate this expected hazard. Similar to
Sunday morning, the chance for near or at freezing temperatures in
the southern Rouge and Illinois valleys remains, but is slight (5-
10%) and is not enough to support additional warnings for those
areas.

A warm front will bring another round of activity on Monday, with
showers arriving on the Oregon coast in the early hours of the
morning and moving eastward through the day. Amounts look
inconsequential, with a quarter to half an inch of rain over coastal
areas and 2 to 6 inches of snow over the Cascades through Monday.
This front will also bring gusty winds, especially to areas east of
the Cascades. A Wind Advisory will be in effect on Monday from 11 AM
to 8 PM for northeast Lake County as gusts exceeding 40 mph are
expected in this area.

Post-frontal showers will continue over the Oregon coast and the
Cascades through the day Tuesday, but conditions look to be stable
otherwise. Temperatures will start to warm as the upper trough moves
away to the east. Afternoon gusty winds will be present east of the
Cascades again, but are not forecast to reach Advisory levels.
-TAD

LONG TERM...Wednesday through Sunday night.
The boundary between the short term and the long term is very
appropriate today, with the the slow-moving trough exiting our
region, and broad high pressure centered offshore building in for an
extended stay. Lingering low level moisture is expected to produce
early morning stratus in Douglas and Josephine counties, including
Roseburg, Cave Junction, and Grants Pass. Otherwise, after another
chilly morning, a pronounced warming and drying trend will get
underway during Wednesday.

This warming will be most significant in southern Curry County with
a Chetco effect of downslope warming expected to produce highs in
the lower 70s for Brookings on Wednesday, lower 80s on Thursday, and
lower 70s into Friday morning before the low level flow turns
onshore. The peak of this warming trend at the coast is expected on
Thursday. Elsewhere, today`s highs at 20 to 25 degrees below normal,
in the lower 50s on the west side and lower 40s on the east side,
will seem a distant memory with Wednesday highs near normal at other
portions of our coast, and several degrees below normal for inland
sites. The warming will be kicked up a notch or two for the
remainder of the long term, Thursday through Sunday, with lows above
normal, and highs around 10 to 20 degrees above normal. The swing in
temperatures from this weekend to next weekend will be in excess of
30 degrees, with the peak of this very strong warming trend expected
at inland locations on Saturday.

A trough is likely to approach the area on Sunday, Day 7, with only
slight cooling.  The speed and position of this trough will be the
main determinants in whether a risk of showers and thunderstorms
develops on Sunday or holds off until Monday/Day 8.

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory from 11 AM to 8 PM PDT Monday for ORZ031.

CA...Freeze Warning from 2 AM to 9 AM PDT Monday for CAZ080-081.

PACIFIC COASTAL WATERS...Small Craft Advisory until 8 PM PDT Monday
     for PZZ350-356-370-376.

&&

$$